Advice: is my PCM shot?
 

I have a 2002 v6. It needs to pass CA smog inspection but the check engine light is on, so it won't pass. It's at the mechanic right now to eval the check engine light; the diagnosis is a bad PCM. I want to verify myself, if possible, whether the PCM is indeed bad or not. And if so where is best to get another one.

**My questions:
1) based on the symptoms below, does it sound like my PCM is bad? If it's not clear based on these symptoms, is there anything else I can check on my own to verify whether or not the PCM is bad?
2) if the PCM is indeed bad, what's the best way to get another one? Are they made by GM anymore? Or do I have to get a junkyard or rebuilt PCM?

**Symptoms:
- Check engine light on.
- TWO CODES = P0403 (Exhaust Gas Recirculation Circuit Malfunction) & P0404 (Exhaust Gas Recirculation Circuit Range/Performance).
- Mechanic says the PCM control for the EGR should send 2 voltage signals, one constant and one variable. He said the constant signal is absent, the variable signal is present. Their troubleshooting diagram says if the constant is absent it indicates a bad PCM. Otherwise the PCM seems fine.
- The car has NO apparent issues when driving, it runs great.

**Any advice on the questions above is appreciated!

Thanks,
Selena

i been lookin at this place INTENSE Racing: INTENSE™ Reprogrammed 3800 Powertrain Control Module (PCM)

Depending on how the mechanic check for voltage, it is possible there is an open between the PCM and the EGR valve. It all depends if he check the 2v just at the EGR or if he checked it at the EGR and at its source. In laymen’s terms the wire or connector broke between the PCM and the EGR valve.

Getting a PCM is not a big deal, there are model numbers on them and if you can find the right model number then comes the hard part, flashing it. The model number defines the hardware but the flashing is the software. Someone with HP tuners software could back up you existing PCM and Flash the new hardware and you would be down the road. Dealers can do this but they charge way more just for the flashing and they won’t want to deal with used parts.

Craby’s solution is probably the best. Make sure the tuner knows this requires all emission (I assume you do) he may not care about the 2V reference signal because many of his PCMs will be sold with EGR delete built in.

There is a small chance the wire going to the EGR valve wire is shorted. If that is the case you could fry a second PCM. The test would to to with everything (PCM and EGR) disconnected to Ohm out the wire to ground.


Good luck

PCMs very rarely go bad. It is far more likely a wiring problem. Did the mechanic test for continuity of both the light blue and gray wires from the pcm connectors to the EGR valve connector? The light blue wire goes to pin 4 of PCM connector C2 (clear). The gray wire goes to pin 32 of PCM connector C1 (blue). These are for a 2000 year. I am think they are the same as a 2002.

The full GM service manual for a 2000 car is here:
http://www.mediafire.com/file/21djvr...bookmarked.pdf

By the way, the "constant" signal is just a ground. Even if that pcm connection was bad internally to the pcm, you could just connect the gray wire to any engine or chassis ground instead of to the PCM.

Excellent, thank you all for this advice. It sounds like there are a couple of things I can check on my own to verify whether it's the PCM or wiring. And it sounds like if I do need a PCM it shouldn't be too bad to get another one. I'll give the suggestions above a try. Fingers crossed I get a more clear answer!